chunk1=[]
chunk2=[]
for i in range(20):
    chunk1.append(i)
print(f"原结果{chunk1}\n{chunk2}")
chunk2=chunk1[:]
print(f"复制后结果{chunk1}\n{chunk2}")
print(f"C2前三元素{chunk2[0:3]}")
print(f"c2后三{chunk2[-3:]}")
begin=(len(chunk2)//2)-1
end=(len(chunk2)//2)+2
print(f"c2中间3{chunk2[begin:end]}")
print(f"c2中间3{chunk2[(len(chunk2)//2)-1:(len(chunk2)//2)+2]}")